The technology of the present disclosure relates to a display body using surface plasmons and a method for observing a display body.
In order to protect, from other persons, values or information of products such as valuable securities, certificates, brand-name products, high price products, electronic devices, and personal authentication media, it is desirable that the products be difficult to counterfeit. Therefore, in some cases, such a product may be attached with a display body that is difficult to counterfeit.
As a display body that is difficult to counterfeit, there is known a display body for displaying image information by using a plurality of cells formed by diffraction grating. With respect to such a display body, there is also known a display body having a micro-image that corresponds to a bitmap pattern having two or more values inside a specific cell among a plurality of cells and can be observed by using a microscope (refer to, for example, Japanese Laid-Open Patent Publication No. 2008-83226).
However, a micro-image corresponding to a bitmap pattern having two or more values displays an image by two or more height differences. For this reason, for example, when dust or a stain having the same size as the height difference constituting the micro-image overlaps with a part of the micro-image, there is a possibility that an observer of a display body falsely recognizes the dust or stain as a part of the micro-image.